Hi... I am turning my Cannondale into a single speed and I really like the look of the 6700 / 6750 grey crankset...

I am going to order up the 6750 Compact crankset because it has the 50t outer ring and use it with a single rear cog properly spaced on a shimano 9/10 speed freehub. (I will also be getting a chain tensioner...)

Here are some questions I have....

1. Can I run that Ultegra 6750 crankset (Pictured Below) with just the outer ring? If so, what will I need?

2. With the 50 tooth front ring I assume I will need about a 19-20 tooth cog on the back... will I have a problem putting a large cog like that so far spaced out for the chain line? (I am aware that one limit may be if it hits the rear stay, but I'm more concerned about load on the freehub)

3. For the rear cog, do I just take a couple old cassettes apart and use all the spacers with the particular cog I want then throw on the lock ring?

4. What chin tensioner does everybody recommend? I don't want to buy a $150 one but I don't want to waste my time with a crummy $10-20 one that sucks.... I hear that both shimano ans surly make a good one but which model and are they both fully adjustable??

Thanks!
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Taking off the chainring is easy, I am sure you can figure it out. But the only way to get the chain into a straight line will be to run a single speed chain tension. They are a pain in the butt, and usually don't work all that great. better idea would be to sell the Ultegra, and get a nice single speed/fixed crank.

Been there... Done that... I know that getting a single speed crank would be easy but that's boring... I chose this crank because of its style... The chain tensioner has nothing to do with a straight line.. It just accounts for the vertical dropouts... The straight lines comes from spacing out the rear cog (it's all explained in the original post) Unless you are referring to a special chain tensioner that also adjusts chain line... But that's a little too close to a derailleur...

I have already built numerous single speed bikes but none using an aluminum frame with vertical drops...

If you read the original post you will see that I have asked four specific questions,

Thanks =)

1. You should be able to run just the 50 tooth ring on that crankset. Either get some SS-specific chainring bolts to replace the stock bolt, or use some chainring bolt spacers to take up the room of the inner chainring. It's just the outer ring that is bizarre, not the spider.



2. Using a 19-20 tooth sprocket is not a problem for the freehub body.

3. Don't just use the individual cog from a multi-speed cassette-the engagement splines are very narrow and will eventually wear some nice notches into the freehub body splines. Plus, they are ramped and can cause the chain to get thrown more easily. Just get a spacer kit with nice alloy spacers and a suitable SS mtb cog, like this: https://mikesbikes.com/product/surly-...e-cog-3317.htm

4. I have never used a derailleur hanger chain tensioner, just an eccentric hub and BB-mounted chain tensioner. You could always take an old derailleur and remove the lower pulley so that you can fold the cage in half and just use the remaining upper pulley as a tensioner. I can't find any photos of this, but my old co-worker did it and it worked beautifully.

Thanks!!! That answered most of my questions,

Any other feedback from other users on what to use as the chain tensioner??

thanks!

Performance sells a kit that has the tensioner, some cogs and spacers. The cogs aren't as nice as the Surley recommended above.

https://www.performancebike.com/bikes..._1031512_-1___

Tensioners are worth what you pay for them. Unlike many other things in life.

When I was about get one I had settled on the Alfine. But I'm not sure it will work if your cog is really far outboard.

If I was putting 20 miles per day or more on a bike I'd get the Paul. If 20 miles per week I'd buy a cheap one.